Lori Boyajian-O'Neill: Testing for Down syndrome is showing advancements

Down syndrome is a genetic disorder which occurs in about 6,000 live births in the U.S. every year. It was named for English physician John Landon Down who cared for children with the syndrome that now bears his name.

Down syndrome is a genetic disorder which occurs in about 6,000 live births in the U.S. every year. It was named for English physician John Landon Down who cared for children with the syndrome that now bears his name.

Tests conducted during the prenatal period provide parents-to-be with information about the risk that their baby will be born with Down syndrome. British physicians have developed a blood test which is more specific and sensitive than current blood tests to assess risk for Down syndrome.

Detecting Down syndrome, what do you know?

T or F:

1. There are current no blood tests for Down syndrome.

2. Ultrasound provides definitive diagnosis of Down syndrome.

3. Amniocentesis is used to screen for Down syndrome.

Human beings have cells which typically have 46 chromosomes. Chromosomes are paired and numbered 1 through 46. In Down syndrome there is an extra copy of the 21st chromosome. Consequently, Down syndrome is also referred to as trisomy 21.

The genetic changes in the cells lead to physical and intellectual disabilities associated with Down syndrome. Children with Down syndrome have characteristic physical attributes including short stature, small hands and ready, beautiful smiles.

Down syndrome cannot be prevented. Identifying risk for Down syndrome provides parents-to-be with information about the risk that their baby will have Down syndrome. Up to 25 percent of pregnancies where the baby has Down syndrome end in miscarriage or stillbirth. Advanced maternal age is a major risk factor. If the age of the mother at the time of delivery is 25 one baby in 1,250 has Down syndrome. Delivery at age 40 increases the incidence rate to 1 in 106. Because younger women have more babies than older women, 80 percent of Down syndrome births are to mothers younger than age 35.

A pregnant woman endures a multitude of tests to monitor her health and that of her baby. Among them are blood tests to screen for a variety of disorders including Down syndrome. Currently, blood testing occurs in late first or early second trimester of pregnancy. If the screening tests suggest high risk for Down syndrome the parents-to-be may want to gain more information from high level ultrasound and addition blood tests. They may also decide to undergo invasive tests such as chorionic villus sampling and amniocentesis. CVS involves a biopsy of the placenta, and amniocentesis involves sampling the fluid around the baby. The goal is to gain genetic information which may indicate Down syndrome, but there are risks for injury to both the mother and baby.

Historically the safer, noninvasive maternal blood tests are not as accurate as CVS or amniocentesis. British researchers have now developed a much more sophisticated maternal blood test to detect Down syndrome which may obviate the need for CVS or amniocentesis. The test, cfDNA, which stands for fetal cell free DNA, is more sensitive and specific than current blood tests. Basically it detects fetal blood cells in the mom’s blood and analyzes for evidence of Down syndrome. This may provide an alternative to the invasive CVS and/or amniocentesis procedures.

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Many parents-to-be want to know as much about their baby as possible, from gender to any abnormalities. Do we paint the room pink or blue? Others do not want to know anything about their baby aside from size and heartbeat. Modern medicine is capable of providing a lot of information through blood tests, ultrasound and other procedures. Time will tell if the cfDNA test is a major step forward for prenatal testing for Down syndrome, but results are very promising.

Answers: 1. F; 2. F; 3. F.

Dr. Lori Boyajian-O’Neill can be contacted at lori.boyajian-oneill@hcahealthcare.com.